Logan Ranger Exo-Arm Team

2017 EXO ARM STUDENT TEAM

Completed Exo Arm

Exo Arm Links:
Exo Arm Fabrication YouTube Video: https://www.youtube.com/watch?v=9mb73gipbu8
Exo Arm Blog: http://loganrangerexoarm.blogspot.com/
District Promotional Video with Exo Arm:  https://www.youtube.com/watch?v=woDyV5qB-Co
WXOW TV: http://www.wxow.com/story/35569252/2017/06/01/logan-students-demonstrate-completed-exo-arm-project
La Crosse Tribune Article: http://lacrossetribune.com/news/local/logan-high-school-students-design-and-build-industrial-exo-arm/article_c024729e-cb81-56bc-8fde-ebfe460aad6d.html
Channel 25/48 TV:  http://www.wiproud.com/news/local-news/project-lead-the-way/729410480
WKBT TV: http://www.news8000.com/news/education/la-crosse-students-build-exoskeleton-arm-to-help-manufacturing-workers/525362743


DESIGNED AND FABRICATED BY LACROSSE LOGAN HIGH SCHOOL 
DIGITAL ELECTRONICS CLASS:

TRENT HERLITZKA
BEN LEDOCQ
MARCUS JARRETT
ALEX MAGNUSON
MASON PARKHURST
TAREN PARMENTER
BRAD VANDENBERG-DAVES
VAENG VANG
JOHN VUE
ANDY KLINGE
ALEX REDMAN
AUSTEN WUENSCH

INSTRUCTOR: STEVE JOHNSTON, LOGAN TECHNOLOGY & ENGINEERING DEPT.

THIS PROJECT WAS MADE POSSIBLE BY:
A GRANT FROM THE LACROSSE PUBLIC EDUCATION FOUNDATION -RANDY AND JUDY EDDY FUND.


CONTRIBUTORS (TECHNICAL EXPERTISE):
DAVE FOYE,  ELECTRICAL ENGINEER
JUSTIN PITZ, LOGAN HS TECHNOLOGY & ENGINEERING INSTRUCTOR  
BILL BANDISH, MOTION INDUSTRIES
MIKE KARLOVICH, TRANE ENVIRONMENTAL, HEALTH & SAFETY MANAGER
JESSE POTRATZ, SCHAEFFLER GROUP USA
STEVEN KLEINHEINZ, SCHAEFFLER LINEAR DIVISION
MIKE WETTSTEIN, INDUSTRIAL AUTOMATION
PETE THEIS, P T WELDING & DRIVESHAFT REPAIR, INC
TERRY CURTIS, LOGAN HS TECHNOLOGY & ENGINEERING INSTRUCTOR

TEACHER ASSISTANT:
GRANT SIMMONS

SPECIAL THANK YOU TO OUR EXO ARM SPONSORS!

Wiring Completed on Exo Arm

Wiring Completed on Exo Arm

Date: 5.30.17
Location: Logan High School
Time: 6 hours
Goal: Complete wiring and install newly constructed circuit board to drive the linear actuator circuit.

The completion of the project is near. We spent quite a bit of time over the last few days working out the problems with the 18v15 motor driver and circuit needed to control the linear actuator. We needed to control the actuator with a winch switch so the operator could vary the height of the arm. This presented some interesting challenges as the motor driver needed an input circuit designed and built to interface with the switch. In the pictures below you will see the progression in getting that circuit up and running.

We also tested the Exo Arm for the first time in a grinding operation. Everything worked as designed so we were pleased. We now have to test at different heights and vertical operation.

Grant testing out the Exo Arm.

Our first attempt at the motor driver input circuit. It worked but the half H-Bridge did not support enough amperage to drive the linear actuator completely. You get an idea of the scale of what we are working with and it is all hand soldered.

Testing out the circuit for the motor driver.

Using a bread board to prototype the circuit first.

Circuit board is completed, now we just clean up the wiring and we are ready to go.

Wiring schematic for switch motor driver circuit.

Wiring schematic for signal motor driver circuit.

Exo Arm Work Day 5.23.17

Exo Arm Work Day 

Date: 5.20.17
Location: Logan HS
Time: 3 hours
Goal: Clean up wiring and work on linear actuator switch.

All test connections from Thursday night were soldered together and shrink wrapped to ensure connectivity. Additionally, a platform for the motor driver was fabricated and installed in the control box.

We placed an image of the initial motor driver circuit toward the bottom of this post to show how streamlined and efficient the initial circuit looked. It was unfortunate that the driver chip would only support 1 amp. We did look for a replacement  chip that would fit in that socket, but were unable to locate any that would output up to 3 amps. Using a full H-Bridge would support the amperage, but require a total redesign of the circuit. This we do not have time for.

Also below you will see a picture of a DPDT switch that is wired to act as a center off rocker switch. We used this to test the linear actuator to see if it had an adequate amount of torque to move the arm up and down the linear rail. We wired it directly into the 12 v line and to our surprise it did lift the arm with no problem. This is in spite of no bearings being used on the rail. Reversing the actuator down caused some jerking which we feel is due to how the arm is balanced on the rail system. Overall, we are pleased that the actuator has enough torque to do the job.

Next we need to wire the momentary switch into a motor driver. The switch is giving us some problem because it is a 3 pole momentary switch. If it was a standard DPDT with 6 pins we would be better off as far as the wiring is concerned.

Wiring getting cleaned up in the control box.

DPDT center off switch ready to be wired in for a test.

Original motor driver circuit. It worked great as long as the actuator did not pull more that 1 amp.

Exo Arm Work Night 5.19.17

Exo Arm Work Night 

Date: 5.19.17
Location: Logan HS
Goal: Connect and test the timing circuit and fix the issue we are having with the linear actuator circuit not supplying the actuator with 12 VDC and stalling out.
Time: 3.5 hours
Students: Grant and Ben


Tonight we wanted to test out both the timer circuit and get our linear actuator running the way it was supposed to. We only got one of these done (timer circuit) but we did find the problem with the actuator.

The actuator circuit is driven with a half H-Bridge. It really is a very simple design that started out complex but Grant broke it down in a very nice solution. The problem was the H-Bridge will max out at 1 Amp. The linear actuator can draw up to 3 amps continuous and a 10 amp peak. So we had a driver for our linear actuator that was not supplying enough current.

The best solution we had was to insert in a Pololu 18v15 Motor Driver I had and try to wire it into the switch. We worked on the logic for while and hooked the system up. It would drive the actuator but not the way we wanted it to. We tried another configuration and accidentally connected a 5 V input to a 12 VDC connection and fried the chip. This happened at about 7:30 at night and we were all getting pretty wore out from trying to solve the problem.

We had a lot planned for the short time we had and that probably cost us one of our motor drivers.  When working into the evening, everyone is tired and we were not as alert as we should have been in checking out faults when wiring in a new motor controller.

The timer circuit on the other hand worked nicely. The whole purpose of this circuit is to allow the operator time to get both his/her hands on the grinder before it starts up for safety reasons. The potentiometer allows us to adjust the time delay to whatever we want it to be. Right now it is at 3 sec. The switch and e-stop will get placed in series over the weekend to complete that circuit.

I ordered another motor controller so we can install it next week and hopefully get the linear actuator working.

Mr. Foye looking over a Ben's soldering job.

Looking down at the control box.

Grant working on some components.

Testing out the wiring of the receptacles.

If you look closely at the chip where the pen is pointing you will see the burned out chip. Look for a white scorch mark.

Ben successfully testing the delay in the grinder turning on.

Grant working on parts in the control box.

Exo Arm Work Night 5.12.17

Work Night
Date: 5.11.17
Location: Logan High School
Time: 3 hours (4-7:00)
Goal: Complete the wiring and begin building the E-Stop control circuit and delay.

Tonight we worked on completing running a different kind of conduit and pulling wires through it. This sounds easy on the surface, but we solder each wire connection in a grounded junction box, wire nut the connection and then use electrical tape over the wire nut to ensure it will not come unscrewed. The conduit is a new plastic flex conduit which protects our wiring running from the box looks surprisingly good on the arm.

Ben and Grant worked with Mr. Foye on two different circuits/boards that we needed. One to control the actuator and the other to allow the E-stop, relay and timer delay circuit to connect. This circuit is being soldered up after we tested it.

We are anxious for our next work night which will allow us to hopefully connect everything and test the system on the arm.

Grant testing his circuit.

Ben and Mr. Foye designing the timer and delay circuit.

Grant soldering a connection.

Pulling wire through conduit.

Soldering connections.

Testing the timer circuit.

Running wire through conduit.

Circuit Design Progress

Date: 5.10.17
Location: Logan HS
Time: 2 hours
Goal: Design and test the delay circuit and linear actuator circuits.
Students: Grant and Ben

We need a delay circuit for the grinder operation. We would like about a 2 second delay between when the grinder is turned on to when the operator begins to use it. This is to allow the operator to get both hands safely on the grinder. We are using a 555 timer in the circuit and used the RC time constant formula to help calculate the necessary components.

In the video below you will see when the two wires are connected (simulating a switch on the grinder) a LED will light up appoximately 2-3 seconds after the circuit is closed. This will give us the delay

The control circuit for the linear actuator has been bench tested. What you will see in the video (if you look at the multimeter to the left side of the frame) is the voltage changing as the switch is depressed. This indicates the switch we are using works and the multimeter takes the place of the linear actuator to show a voltage is sent to it. The switch also has a built in LED.

Saturday Work Day 5.6.17

Wiring Exo Arm Conduit and Control Box

Date: 5.6.17
Location: Logan HS
Time: 5 hours
Goal: Pull wire though conduit and reconfigure the control box for another receptacle with main power switch.


We needed to get a lot of the wiring done today so we can connect to the main circuit board and begin to test the electronics. Much of today was spent fabricating covers, attaching boxes, measuring wire and conduit, finding places to connect and attach everything without taking away from arm functionality.

The metal flexible conduit we saved from last years project came in handy. We tried some other types of conduit, but they were not flexible enough. This material is very flexible for a metal product. Pulling wire though flexible conduit is a challenge so we fished the wire though. The flex connectors that were used to connect to the arm and electrical boxes seem to hold the conduit firmly yet allow for arm movement. Plastic inserts were placed in the ends of the conduit to protect the wire from the sharp edge.

16 gauge wire was run through the conduit along with the power cable for the grinder. This will have to be terminated in the junction box we attached.

Control box is ready for more additions. The GFCI box was a tight fit and that receptacle is so much bigger than a regular receptacle, we had to go out the top of the box with 90 degree elbows and EMT pipe. The larger quad  box is where we will mount the relay.

Work night planned on Thursday.

Linear actuator and pipe attached to the mounting plate.

Close up of linear actuator and mounting placement. The 1/4" bolts will be replaced with graded.

The plastic control box had to be trimmed to receive the electrical boxes and wiring.

Cutting EMT pipe for conduit.

Electrical boxes mounted.

Receptacles wired in.

Getting ready to wire the grinder switch back to control box.

Hole drilled in with grommet for grinder power cable.

Box mounted on underside of arm.

Wire running through grinder arm.

Showing how conduit is attached. A metal cover was fabricated to hold the flex connector.

Arm with wire pulled through conduit to electrical box.

Exo Arm Work Night 5.4.17

Exo Arm Work Night

Date: 5.4.17
Location: Logan HS
Time: 3.5 hours (4-7:30 PM)
Students: Alex R., Alex M., Grant, Trent and Ben.
Goal: Begin to wire in the electronics for the Exo Arm.


Our goal of getting most of the wiring done tonight fell short. We spent at least an hour discussing wiring possibilities and exploring the option of a 2 second delay using a 555 timer before the grinder actually turns on. Also, part of the existing wiring for the GFCI had to be redone to allow for another switch and separate receptacle for our 12 V power supply. Regardless we made progress and have a new parts list to pick up.

The good news is the linear blocks that we fabricated (thanks to Mr. Pitz) seem to secure the arm to the rail with no deformity to the rail or block. No bearings are used in these so they will need some grease to work well.

Filing down rough or sharp edges were taken on by Alex R. and Alex M. This is really an important job because in the production of the arm we are sure to have forgotten some sharp edges so having another set of eyes go over it again really helps.

We determined that the wire gauge we will be using is 18 GA to ensure we have enough wire to carry the current without melting anything. Much discussion went into the location of the grinder switch and how it will be mounted. We decided to mount it near the grinder and then experimented with different conduit to see which one allowed for the most freedom of movement. We got some blue plastic tech conduit that we thought would work well but it did not. A piece of metal flex conduit will be used along the bottom of the arm.

The warning light at the top of the rail was wired in to a switch and tested out to perfection. The toggle switch to operate the linear actuator was tested but we could not get it to work. We suspect we have it wired wrong and need a jumper somewhere on it. The circuit for the linear actuator did not work as expected. We need to bring in a 6 V power source for it somewhere.

Work night next week will focus on more wiring and troubleshooting.

Trent stripping wires.

Alex R. filing the arm down.

Ben working with Mr. Foy on the relay circuit using transistors. More work needs to be done on this.

Filing the aluminum base.

Alex M. cutting a piece of aluminum for the grinder switch.

The newly machined bearingless linear blocks.

Trent getting some wires stripped.

Box and Panel Fabrication

Box and Panel Fabrication

Date:5.2.17
Location: Logan HS
Time: 2 hours
Goal: Begin to mount components in box and fabricate switch panel.

Our primary concern right now is the bearings on linear rail supporting the working load of the Exo Arm. We have been in contact with Schaeffler engineers to see they have a manufactured solution for us. We feel we either need to get an all metal bearing or machine out a new bearing block without a bearing in it. Special thanks to Schaeffler engineers as they are working on a solution from their end.  Mr. Pitz and Taren got to work on a new bearing block that we hope will only be needed as a backup.

The 15 amp GFCI outlet will be our fuse in the system.  That was mounted to the wall of our electrical box. We tested it and it works as advertised. We also put standoffs on our 12 V PS to keep airflow around it while it is working. This will be mounted to the side of the box.

GFCI mounted in place on box wall.

12 V PS with standoffs attached to allow for air flow.

Grant getting everything labeled on his motor control circuit.

Test block machined out to fit over the linear rail. It rode nicely on the rail, but we do not have a load on it yet.

Piece of aluminum bent up and being  drilled out  for switches.

Wiring the Electrical Requirements Begins

Wiring of the Electrical Requirements Begins

Date: 5.1.17
Location: Logan HS
Time: 3 hours
Goal: Purchase electrical parts and begin to assembly the control box.

Part of Saturday AM was spent at Menards looking for electrical boxes, connectors, wires, termination devices, wire protection...etc. We want to begin wiring the linear actuator into the system right after it is mounted so we purchased a large plastic electrical box ( we have used something similar before) to enclose all the components.

Right away we ran into problems with the thickness of the wall of the box as it was almost too thick for mounting a metal box where our 15 amp GFCI will be. We needed to modify the way we mounted the box slightly. The GFCI will be our circuit breaker instead of running a separate breaker for the system.

Someone donated a heavy gauge 3 wire electrical cord a while ago that we are repurposing for our power plug which will run into the GFCI.

Next step is to mount the 12 V power supply and then wire in a bus for our lights which also run on 12 V.

Raw materials before we begin connecting

15 amp plug attached to our wire.

15 Amp GFCI protected by a metal box and bolted to the plastic wall of our larger component box.

Work on Exo Arm Base Moves Forward

Work on Exo Arm Base Moves Forward

Date: 4.27.17
Location: Logan HS
Time: 3.5 hours
Goal: Fabricate a base that will support the linear rail assembly.


Work on the base has moved at a rapid pace. Based on the wooden prototype base we extracted measurements to help us determine the angles and lengths we needed to attain stability. The 3 x 3 aluminum tube stock provided a nice welding and bolting surface for Mr. Pitz and his students to build off of.

A aluminum plate platform has been bolted on to mount the linear actuator and electronics. We are concerned about the stability of the arm when moving right or left. We feel we may need to strengthen the back support or increase the base support under the platform to help stabilization. The front to back motion is well supported by a diagonal brace that was installed.

We may need to replace one of our linear bearings that mounts on the rail system. We noticed some wear and tear on it. The bearing is designed for a different type of load. We are using it in a vertical application which puts more stress on the bearing. This is not a manufacturer defect, but a result of the application we are using it in. Calls have been made to our supplier to see if a metal bearing is available instead of a plastic one.

Plate and arm being bolted to the base.

View from the back which shows the angle support and weight holder.

I know this does not look good, but the 2 x 4 just hold the arm in place until we install the linear actuator.
The arm is contracted back toward center mass and secured with velcro.

Another view of base assembly.

Add caption

Taren welding the base

Taren welding the base.

Picture of linear bearing that has experience some wear and tear toward the opening. Again, we do not feel this is a manufacture defect, but a result of the application we are using it in.